Common and Preferred Stock, Stock-Based Plan Descriptions and Share Information (Details) (USD $)	12 Months Ended			12 Months Ended				1 Months Ended	0 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 LTICP 2010 [Member]	Dec. 31, 2011 Non-vested Stock [Member]	Dec. 31, 2011 Stock Options [Member] Y	Dec. 31, 2010 Stock Options [Member] Y	Dec. 31, 2009 Stock Options [Member]	Jan. 31, 2011 Certain Officers, Key Employees, and Directors [Member] Non-vested Stock [Member]	Jul. 05, 2011 Certain Officers [Member] Non-vested Stock [Member]	Dec. 31, 2011 Director [Member] Stock Options [Member] LTIP [Member]	Dec. 31, 2011 Office and Employees [Member] Stock Options [Member] LTIP [Member]	Dec. 31, 2011 Employee Stock [Member]
Stock-Based Compensation [Line Items]
Number of shares available for future grants			1,728,489
Stock-Based Compensation [Abstract]
Number of stock-based plans	2	2
Number of shares granted								145,002	40,000
Service period (in years)				3 years
Discount rate of ESPP (in hundredths)	5.00%
Stock-Based Plan Descriptions and Share Information [Abstract]
Amount rounded for calculation in exercise										0.125	0.125
Expiration period, maximum										10 years	10 years
Annual vesting percentage											33.30%
Stock options activity [Roll Forward]
Outstanding, beginning of period (in shares)					134,070
Exercised (in shares)					(39,700)
Forfeited (in shares)					(300)
Outstanding, end of period (in shares)					94,070	134,070
Exercisable, end of period (in shares)					90,570							432,756
WEIGHTED-AVERAGE EXERCISE PRICE
Weighted average exercise price, outstanding, beginning of period (in dollars per share)					$ 21.32
Weighted average exercise price, exercised (in dollars per share)					$ 21.77
Weighted average exercise price, forfeited (in dollars per share)					$ 22.25
Weighted average exercise price, outstanding, end of period (in dollars per share)					$ 21.12	$ 21.32
Weighted average exercise price, exercisable, end of period (in dollars per share)					$ 21.03
WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM
Weighted average remaining contractual term, outstanding, beginning of period (in years)					11.04
Weighted average remaining contractual term, outstanding, end of period (in years)					14.92	11.04
Weighted average remaining contractual term, exercisable, end of period (in years)					15.34
AGGREGATE INTRINSIC VALUE
Aggregate intrinsic value, outstanding, beginning of period					$ 1,266,000
Aggregate intrinsic value, outstanding, end of period					1,597,000	1,266,000
Agregate instrinsic value, exercisable end of period					1,546,000
Total intrinsic value of options exercised					$ 500,000	$ 1,100,000	$ 400,000